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Thursday, September 3, 2015

The Past Was Horrifying - Sounds of the Mesozoic

Okay, welcome to my part 2 of X on how the past was likely horrifying if we had lived through it. Today is going to be about what the Mesozoic Era might have sounded like. Apologies ahead of time but this will be a video-heavy post.

When we picture (or rather hear) what dinosaurs (and other prehistoric reptiles) may have sounded like most people will think back to dinosaur movies where the beasts are rampaging. Roaring, snorting, growling, and hissing creatures fill the screen with angry sounds. After the release of Jurassic Park, many of the sounds created by Universal's sound studio have been remixed and reused by other films both on large and small screens. Let's quickly review some of the iconic sounds that these creatures made back in the early 1990s.

Tyrannosaurus breaks out of its pen. Prepare to get T. rekt. Copyright Universal Studios.

The famous scene with Velociraptors in the kitchen. Copyright Universal Studios.

This gives us a great variety of sounds. From the deep bass rumbling roar of the Tyrannosaurus to the chirps of the Dilophosaurus, and the high-pitched screech of the Velociraptor we have great mood-appropriate sounds from our animal villains and protagonists. I especially love the sounds that the Tyrannosaurus in Jurassic Park makes. It gave me chills in the theater all those years ago and it still is exciting to me. But it also makes me question whether an actual Tyrannosaurus sounded like its cinematic depiction.

Since Tyrannosaurus and the other dinosaurs depicted in Jurassic Park are archosaurs, I figured it would be a reasonable place to start looking at the sounds our extinct friends might have made. If we can use extant phylogenetic bracketing for integument and parental care (among other things), why not the possible vocal capabilities? I decided to look at crocodiles and ratites + hoatzin, as my EPB.

What I found was frightening. The first thing I learned is that ratite sounds are not cute.

A modern Rhea, doing Rhea things.

Ostriches with their absurdly low booming sounds.

The frighteningly unexpected growls of the modern Cassowary.

The Hoatzin. Long video, but you can hear the sharp, chuffing near the start between parrot calls.

Being the glutton for punishment that I am, I decided to make myself listen to crocodilian sounds. Not only are they equally terrifying, but they also share some similarities to some of the ratite sounds.

Crocodilians have primeval sounding roars and the occasional hiss.

What is the takeaway from this investigation? For me, it is the idea that screeching, chirping, and otherwise boisterous dinosaurs may not be as plausible as Hollywood would like us to believe. Both croc and modern less-derived birds generally do not make "songs" or "calls" but rather deep rumbles/roars and occasional hisses/clicks. The shriek of the Jurassic Park Velociraptor, spliced together with dolphin and monkey sounds doesn't seem so plausible to me. Nor does the pretty sounding cry of our oddly-hopping Dilophosaurus (or it's rattlesnake-mincing attack cry) make much sense if the similarities between our EPB creatures represent a real signal. But what of our beloved Tyrannosaurus call?

A collection of all the Tyrannosaurus rex sounds from Jurassic Park

To me, this is the most convincing of all the theropod sounds produced for cinema. It sounds the most like the creatures I sampled for my EPB. But there is also another potential problem: size. Just as a tuba sounds deeper than a flute, the size of an animal's resonating chamber (larynx/sirynx) affects the deepness of the sounds it produces. Our largest terrestrial animal today, the African Elephant, is able to produce infrasound (sound too low to hear). The idea of large theropods or sauropods being able to produce infrasound is not itself unreasonable. The large birds and crocs I listened are already producing super-low frequency sounds and crocs are known to produce infrasound during mating season. The Mesozoic world may have been punctuated by low frequency roars and rumbles and silent periods interrupted by a strange feeling in your bones as a large sauropod or theropod let out a noise too low for our ears to hear.

"But wait," my ornithischian fans cry out (Pete, I'm looking at you...)! "What is this saurischian bias?" Well one reason for my saurischian bias is that most (but not all!) movie dinosaurs that make sounds are saurischians. Another is that we have to do a bit less speculation on the possible sounds some ornithischians would have made thanks to Sandia Labs and their 3D reproduction of a Paraaurolophus crest. While not perfect, it gives us an idea of what type of sounds large hadrosaurs may have been able to produce. It is worth noting that this reconstructed vocalization is a low sound, similar to what I've been suggesting for saurischians.

Ignore the metallic overtones...

Compared to the Jurassic ParkParasaurolophus cry...

Moral of the story: the Mesozoic would sound very little like what we imagine it to, based on depictions in cinema and television. Dinosaurs at least would have been making sounds more like their modern relatives than the mixed-up mammal sounds studios are fond of using. This would create an audio landscape deeply unfamiliar to our modern ears.

I'll leave you with one more clip: perhaps the most accurate dinosaur sounds in all of cinema history. Next time from me: discussion of a new tooth paper out in the Journal of Vertebrate Paleontology standardizing theropod tooth nomenclature, an issue near and dear to me at the moment!